Crashing + Access is Denied?

Sometimes when I play league, the game will crash. I used to fix this by just closing it in Task Manager and opening League again. Recently, whenever I try to close League of Legends.exe, it'll give me an error message that says "Access is Denied". I'm the only user on my computer, and an admin. Whenever I try to close it, the fan on my laptop will go crazy and sometimes I'll bluescreen with some "VIDEO_TDR_FAILURE" error.

All of my video card drivers are updated. I've run malwarebytes to check if a virus was causing it, and got nothing. I've reinstalled + repaired the game, and that didn't work either.

Currently, I try to fix this by restarting my computer, which ends the League of Legends.exe process and lets me reconnect. This isn't really that effective, since I end up underleveled and punished by the LeaverBuster system, which puts me in Low Priority queue. Sometimes it'll just crash a second time and I have to restart it.. Again.

If anybody has solutions, please comment. Q_Q